Noncorrosive cleaning composition and process

ABSTRACT

An improved composition and process for cleaning metal surfaces, and particularly aluminum and aluminum alloy surfaces wherein the cleaning is effected by using an aqueous alkaline solution which contains borates as the main alkaline component and, additionally, contain one or more vanadium compounds. Additionally, if desired, the cleaning compositions may also contain one or more non-ionic surface active agents and/or an ionic wetting agents.

Ilnited States Patent Dittel et a1.

July 4, 1972 NONCORROSIVE CLEANING COMPOSITION AND PROCESS Inventors:Friedrich Dittel, Mainz-Kostheim; Peter Jorns, Frankfurt am Main, bothof Germany Assignee: Hooker Chemical Corporation, Niagara Falls, NY.

Filed: Feb. 11, 1970 Appl. No.: 10,626

US. Cl. ..252/135, 23/15, 23/19 V, 252/387, 252/389, 252/539, 260/429Int. Cl ..C23f 11/08, C23g l/16, C23g 1/18 Field of Search ..252/387,389,135,137,138; 23/15, 19 V; 260/429; 106/14 References Cited UNITEDSTATES PATENTS 3/1967 Chisholm ..l06/l5 X FOREIGN PATENTS ORAPPLICATIONS 933,514 8/1963 Great Britain ..252/135 OTHER PUBLICATIONSThe Condensed Chemical Dictionary, Sixth Edition, by Arthur & ElizabethRose, 1962, page 39.

Primary Examiner-Leon D. Rosdol Assistant Examiner-Dennis L. AlbrechtAtt0rneyStanley Lieberstein and William J. Schramm [57] ABSTRACT 10Claims, No Drawings NONCORROSIVE CLEANING COMPOSITION AND PROCESS Thisinvention relates to an improved process and composition for cleaningmetal surfaces and more particularly it relates to an improved processand composition for cleaning aluminum and aluminum alloy surfaces,without appreciable attack or pitting of the surfaces.

l-leretofore, it has been known that metal surfaces may be cleaned byspraying or immersion, using various aqueous alkaline solutions.Typically, the aqueous alkaline cleaning solutions used containhydroxides, carbonates, phosphates, silicates, and borates, as well asmixtures of one or more of these materials, to provide the alkalinity inthe solution. It has been found, however, that when the more highlyalkaline solutions are used, appreciable corrosion, such as pittingand/or discoloration, is frequently encountered in the cleaning ofsurfaces of aluminum, zinc, or their alloys. Although it is known thatthis problem may be substantially avoided by using cleaners based on thealkali silicates, the surfaces cleaned with these materials frequentlyhave extensive deposits thereon which not only detract from theappearance of the metal but also have an adverse affect on subsequenttreatments, such as lacquering, chemical surface treatments, and thelike. Apparently, these deposits consist mainly of silicates which, dueto their insolubility, are not easily removed by rinsing with water.

It has recently been proposed in British Pat. No. 933,514 that theanti-corrosive cleaning of aluminum and aluminum alloy surfaces may beachieved by using an aqueous solution containing about 3 to percent byweight borax in combination with suitable wetting agents. Although withthis composition, the deposits and problems resulting therefrom,obtained when using the silicated cleaners, are essentially overcome,some difficulties were still encountered with respect to corrosion. Itwas found that particularly in the treatment of surfaces which had beenspot welded, there were undesirable corrosive attacks by the boraxcontaining solutions.

It is, therefore, an object of the present invention to provide animproved composition and process for the cleaning of metal surfaces.

A further object of the present invention is to provide improvedcompositions and process for cleaning aluminum and aluminum alloyssurfaces, wherein corrosive attack of the surface by the cleaningcomposition is substantially eliminated.

These and other objects will become apparent to those skilled in the artfrom the description of the invention which follows.

Pursuant to the above objects, the present invention includes acomposition useful for the cleaning of metallic surfaces, whichcomposition comprises an aqueous alkaline solution in which theinorganic alkalizing component is a borate and wherein the compositionfurther contains from about 0.1 to 10 grams per liter vanadium ions,calculated as V. This composition has been found to be particularlysuitable for the cleaning of surfaces of aluminum and aluminum alloysbecause of the substantial corrosion inhibiting effect of the cleaningsolution, but is also very useful for the cleaning of zinc and zincalloy surfaces, as well as ferrous metal surfaces.

More specifically, the compositions of the present invention are aqueousalkaline solutions which desirably contain from about 10 to 100 gramsper liter of a borate. Numerous borate compounds which are soluble inthe aqueous alkaline cleaning solutions may be used. Exemplary of suchmaterials are the alkali metal borates alkali tetraborates, alkalipolyborates, and the like. Of these, particularly good results have beenobtained when using sodium tetraborate (Na B O 101-1 0) and sodiumpolyborate (Na B O, -4H O), so that hereinafter, particular referencewill be made to these materials as being the preferred borates for usein the present composition. This is not, however, to be taken as alimitation on the borate compound which may be used as other boratematerials which are soluble in the aqueous alkaline solutions are alsosuitable.

In addition to the borate compound, the aqueous alkaline cleaningsolutions of the present invention also contain from about 0.1 to 10grams per liter of vanadium ions,,with amounts of vanadium ions withinthe range of about 0. l tov 3.0 grams per liter being preferred. Thevanadium ions may be incorporated in the aqueous alkaline boratesolutions by means of any vanadium compounds which are sufficientlysoluble in the solutions to provide the requisite amount of vanadiumions. Exemplary of the suitable soluble vanadium compounds which may beused are the various vanadates, such as NaVO KVO 4 a, a Qt. Lh M NZ n 4z 1 ih z fi vanadium chloride, vanadium sulfate, vanadium nitrate,vanadium oxide; as well as in the form of vanadyl compounds. Of these,in many instances, the alkali meta-, alkali orthoand alkalipyrovanadates have been found to be preferred. Accordingly, hereinafterprimary reference will be made to these compounds as the source ofvanadium ions in the compositions of the present invention. This is not,however, to be taken as a limitation on the vanadium compounds which maybe used as other vanadium compounds, such as the vanadium oxides andvanadyl compounds are also suitable.

Additionally, it is further to be appreciated that where referenceherein is made to alkali compounds, such as the alkali vanadates and thealkali borates, it is intended that this reference shall include thecompounds of the alkali metals, i.e., sodium, potassium, lithium,cessium and rhubidium. Additionally,for purposes of the presentinvention, it is to be understood that the term alkali shall alsoinclude the ammonium compounds. In many instances, it has been foundthat the sodium and potassium compounds, such as the sodium borates andpotassium vanadates, are the preferred alkali compounds for use in thepresent compositions. This is not, however, to be taken as a limitationon the alkali compounds which may be used but merely as being exemplarythereof.

In addition to the borate and vanadium compounds, the aqueous alkalinecleaning solutions of the present invention may also contain one or moresurface active agents. It has been found, that particularly where thesolutions are used for cleaning very dirty and/or very greasy surfaces,the addition of such surface active agents serve to increase thecleaning effect of the present solutions, thus making them moreeffective.

It has been found that the non-ionic surface active agents areparticularly well suited as additives for the cleaning compositions ofthe present invention. Exemplary of specific nonionic surface activeagents which may be used are mixtures of low ethoxylated lipophiliccompounds and highly ethoxylated condensation products, such as mixturesof alkyl aryl polyglycols with two to six ethylene oxide groups andalkyl aryl polyglycol ethers with 15 to 20 ethylene oxide groups. Withsuch materials, it has been found that the turbidity point of thecleaning solution is about 3 to 10 higher than the temperatures at whichthe solutions normally are used. Additionally, however, anionic surfaceactive agents may also be used, such as the alkyl aryl sulfonates. Thesehave been found to be particularly advantageous in improving the rinsingcharacteristics of the cleaning solutions. In general, where one or moresurface active agents are included in the composition they are desirablypresent in a total amount within the range of about 1 to 10 grams perliter.

In utilizing the aqueous alkaline cleaning solutions of the presentinvention, they are brought into contact with the metal surfaces to becleaned for a period sufficient to effect substantial cleaning of thesurfaces. Although various means may be used for bringing the solutionsinto contact with the metal surfaces, these solutions have been found tobe particularly well suited for immersion cleaning processes, althoughin some instances, spray applications may also be used. Desirably, thecleaning solutions of the present invention are used at elevatedtemperatures, temperatures within the range of about 60 to C beingpreferred. In many instances, effective cleaning has been found to becarried out, without any corrosion, such as pitting or discoloration ofthe metal surfaces, in contact times within the range of about 5 to 10minutes, which times have been found generally to be typical.

In order that those skilled in the art may better understand the presentinvention and the manner in which it may be practiced, the followingspecific examples are given. In these examples, unless otherwiseindicated, parts and percent are by weight and temperatures are indegrees centigrade.

EXAMPLE 1 Aluminum sheets were immersed for minutes at 75 C in anaqueous cleaning solution containing 40 grams per liter of borax. Duringthe treating time, appreciable hydrogen generation was observed and themetal losses on the aluminum sheets by corrosion were found to be 130milligrams per square meter. Subsequently, 0.6 grams per liter ofpotassium metavanadate was added to the cleaning solution. Additionalsheets of aluminum were then immersed in the solution for 5 minutes at75 centigrade. In this instance, no hydrogen generation was observed andthere were no measurable metal losses during the cleaning process.

EXAMPLE 2 Aluminum sheets were immersed for 5 minutes at 75 C in anaqueous solution containing 40 grams per liter of a mixture having thefollowing composition:

Following the treatment in this manner, interference colors were foundon the surfaces of the treated sheets and hydrogen evolution wasobserved during the treatment. Similar aluminum sheets which had beenspot welded were also treated in this solution under the same treatingconditions. During the treatment of these sheets, appreciable hydrogengeneration was observed and after rinsing the sheets, considerable darkdiscoloration on the spot weld was found.

Thereafter, 0.6 grams per liter of potassium metavanadate was added tothe solution. Additional quantities of aluminum sheets, some of whichhad been spot welded, were treated in this solution for 5 minutes at 75C. During the treatment of these sheets, there was no hydrogen evolutionand following the treatment, no interference colors were found on thealuminum surface nor was there any dark discoloration on the spot weld.

EXAMPLE 3 An aqueous solution was prepared containing 35 grams per literborax, 1.5 grams per liter nonyl phenol polyglycol ether containing fourether groups per molecule, 3.5 grams per liter dibutyl phenol polyglycolether containing 50 ether groups per molecule, and one gram per litersodium dodecyl benzene sulfonate. This solution was divided into twoportions, the first portion being designated solution A and the secondportion, to which was added 0.6 grams per liter of potassiummetavanadate, was designated as solution B. In both of these solutions,dirty, oily aluminum and aluminum alloy sheets, as well as sheets ofgalvanized steel and high grade steel were cleaned by immersion for 5minutes at 95 C. During the treatment of the aluminum and galvanizedsteel sheets in solution A, appreciable hydrogen generation was observedand although, after rinsing and drying the sheets were found to bedegreased and cleaned, their appearance was very spotty with a mattfinish. All of the sheets which were treated in solution B, however,were found to be smooth and without spots after rinsing and drying.Additionally, after a throughput of 2 square meters of the metalsurfaces per meter of cleaning solution, no hydrogen generation wasobserved and excellent cleaning of the sheets was obtained.

While there have been described various embodiments of the invention,the compositions and methods described are not intended to be understoodas limiting the scope of the invention as it is realized that changestherewithin are possible and it is intended that each element recited inany of the following claims is to be understood as referring to allequivalent elements for accomplishing substantially the same result insubstantially the same or equivalent manner, it being intended to coverthe invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A cleaning composition useful in the cleaning of metal surfaces whichconsists essentially of an aqueous alkaline solution in which thealkalizing component is a borate in an amount from about 10 to I00grams/liter wherein said borate is independently selected from the groupconsisting of alkali metal tetraborates and alkali metal polyborates andwherein the solution also contains from about 0.1 to 10 grams/litervanadium ions, calculated as V wherein the vanadium ions are added inthe form of a compound selected from the group consisting of alkalimetal metavanadates, alkali metal ortho vanadates, alkali metalpyrovanadates, vanadium chloride, vanadium sulfate, and vanadiumnitrate.

2. The composition as claimed in claim 1 wherein the solution containsfrom about 10 to grams per liter of a borate and from about 0. l to 3.0grams per liter vanadium ions.

3. The composition as claimed in claim 2 wherein the solution alsocontains at least one surface active agent agent selected from non-ionicsurface active agents and anionic surface active agents, in a totalamount within the range of about 1 to 10 grams per liter.

4. The composition as claimed in claim 3 wherein vanadium ions are addedto the solution in the form of a compound selected from alkalimetavanadates, alkali orthovanadates and alkali pyrovanadates, and theborate compound is selected from sodium tetraborate and sodiumpolyborate.

5. The composition as claimed in claim 3 wherein the borate compound isselected from sodium tetraborate and sodium polyborate.

6. A method for cleaning surfaces of aluminum and aluminum alloys, zincand zinc alloys, or ferrous metal which comprises contacting the surfaceto be treated with the cleaning solution of claim 1 and maintaining thesolution in contact with the surface for a time sufficient to effectsubstantial cleaning thereof.

7. The method as claimed in claim 6 wherein the metal surfaces areimmersed in the aqueous cleaning solution.

8. The method as claimed in claim 7 wherein the aqueous cleaningsolutions contain from about 10 to 100 grams per liter of the borate andfrom about 0.1 to 3.0 grams per liter of vanadium ions.

9. The method as claimed in claim 8 wherein the solutions also containat least one surface active agent selected from non-ionic surface activeagents and anionic surface active agents in a total amount within therange of about 1 to 10 grams per liter.

10. The method as claimed in claim 9 wherein the borate compound isselected from sodium tetraborate and sodium polyborate.

2. The composition as claimed in claim 1 wherein the solution containsfrom about 10 to 100 grams per liter of a borate and from about 0.1 to3.0 grams per liter vanadium ions.
 3. The composition as claimed inclaim 2 wherein the solution also contains at least one surface activeagent agent selected from non-ionic surface active agents and anionicsurface active agents, in a total amount within the range of about 1 to10 grams per liter.
 4. The composition as claimed in claim 3 whereinvanadium ions are added to the solution in the form of a compoundselected from alkali metavanadates, alkali orthovanadates and alkalipyrovanadates, and the borate compound is selected from sodiumtetraborate and sodium polyborate.
 5. The composition as claimed inclaim 3 wherein the borate compound is selected from sodium tetraborateand sodium polyborate.
 6. A method for cleaning surfaces of aluminum andaluminum alloys, zinc and zinc alloys, or ferrous metal wHich comprisescontacting the surface to be treated with the cleaning solution of claim1 and maintaining the solution in contact with the surface for a timesufficient to effect substantial cleaning thereof.
 7. The method asclaimed in claim 6 wherein the metal surfaces are immersed in theaqueous cleaning solution.
 8. The method as claimed in claim 7 whereinthe aqueous cleaning solutions contain from about 10 to 100 grams perliter of the borate and from about 0.1 to 3.0 grams per liter ofvanadium ions.
 9. The method as claimed in claim 8 wherein the solutionsalso contain at least one surface active agent selected from non-ionicsurface active agents and anionic surface active agents in a totalamount within the range of about 1 to 10 grams per liter.
 10. The methodas claimed in claim 9 wherein the borate compound is selected fromsodium tetraborate and sodium polyborate.